CVE-2026-15534

What it is

Perl versions through 5.45.1 have out-of-bounds heap reads and writes during regular expression matching via an undersized superlinear cache in S_regmatch. The regex engine's superlinear cache holds one bit per subject position for each participating WHILEM node, so the bit count is the subject length plus one times the number of nodes. Nothing checks that product for positive overflow of the signed 32-bit count: a 286331153 byte subject matched against a pattern with 15 participating nodes stores the count as 14, leaving a two byte cache. The cache is then indexed from the real match position and node number, so reads go past the end of the allocation, and on failure CACHEsayNO sets a bit past it. A caller that matches an attacker controlled subject of this size against a pattern of this shape can crash the process or corrupt heap memory.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. High risk of service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-09 18:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-23 20:10 UTC Last updatedMost recent change to the record

Details

Published

2026-08-09 18:16 UTC

Last modified

2026-10-23 20:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-125 · Out-of-bounds read

Record status

Awaiting Analysis

Attack profile CVSS 3.1 · 5.7

Attack vector

Local

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

High